Rings and Things

The subject of this NASA/ESA Hubble Space Telescope image is situated in the Perseus Cluster, also known as Abell 426, 320 million light-years from Earth. It’s a barred spiral galaxy known as MCG+07-07-072, seen here among a number of photobombing stars that are much closer to Earth than it is.

MCG+07-07-072 has quite an unusual shape for a spiral galaxy, with thin arms emerging from the ends of its barred core to draw a near-circle around its disk. It is classified as an SBc(r) galaxy: the c denotes that its two spiral arms are loosely wound, each only performing a half-turn around the galaxy, and the (r) is for the ring-like structure they create.

Rings in galaxies come in quite a few forms, from merely uncommon, to rare and scientifically important! Lenticular galaxies are a type that sit between elliptical and spiral galaxies. They feature a large disk, unlike an elliptical galaxy, but lack any spiral arms. Lenticular means lens-shaped, and these galaxies often feature ring-like shapes in their disks.

Meanwhile, the classification of “ring galaxy” is reserved for peculiar galaxies with a round ring of gas and star formation, much like spiral arms look, but completely disconnected from the galactic nucleus — or even without any visible nucleus! They’re thought to be formed in galactic collisions. Finally, there are the famous gravitational lenses, where the ring is in fact a distorted image of a distant, background galaxy, formed by the ‘lens’ galaxy bending light around it. Ring-shaped images, called Einstein rings, only form when the lensing and imaged galaxies are perfectly aligned.

Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov